Fluid pressure speed sensing device



1953 H. E. BARRETT ET AL 2,657,699

FLUID PRESSURE SPEED SENSING DEVICE Filed Jan. 29, 1949 INVENTORSHILLAR'D E.'EIARRETT.

SAMUEL J- HALL. WILLIAM E- EEHAFFEH BYVLIREKJW ATTORNEY I is member.

Patented Nov. 3, 1953 ,porationof Delaware UNITED STATES ATENT OFFICE2,657,699 FLUID PRESSURE .SPEED SENSING DEVICE Hillard E. Barrett, EastOrange, Samuel J. Hall,

Lodi, and William C. Schafier,,Fair Lawn, N. J assignors 'toCurtiss-Wright Corporation, a cor- ApplicationvJanuary 29, 1949, SerialNo. 73,562

1-Cla'im. 1

This invention relates to speed sensing mechanisms and is particularlydirected-to such mechanisms providing a fluid pressure which is afunction-of the speed of rotation of a rotating memher.

A primary object of this invention is the provision of a noveland simplespeed sensing mechanism for obtaining a fluid pressure which "is a"function of the speed of rotation of a rotating A further object of theinvention relates to the provision of sucha mechanism in which no fluidpressure seals are necessary between the fixed and rotating parts of themechanism and which is applicable to measurement and/or control of highrotative speeds. Such a mechanism may be used to measure and/or tocontrol-the speed of rotation of an engine or other rotating parts.

Other objects of the invention will becomeapparent upon reading theannexed detailed description in connection with the drawing in which:

Figure '1 is a sectional view through a speed sensing mechanismembodying the .invention; and

Figure 2 is a view schematically illustrating use of said speed sensingmechanism for controlling the speed of rotationof an engine.

Referring to the drawing, a :shaft l0, whose I speed of rotation is tobe sensed extends into a housing I2 of "the speed sensingmechanism,:saidshaft being journaled in said housing by a hearing I 4. ,A guide memberIt has a stem tightly fitted within a bore in the shaft 10 for rotationwith said shaft. Said guidemember I6 also has a-plurality ofcircumferentially spaced notches 18 about its periphery and a sphericalball or flyweight 2!! is disposedin each of said notches. An axiallymovable thrust .member 22 is slidably fitted within thecupeshaped end ofthe shaft Ill. The thrust member 22 is keyed to the shaft ill forrotation therewith ,by a pin 24 extending through the thrust member intoaxially extending slots 26 in the cup-shaped end of said shaft. Thethrust member 22 also has .-a:conical surface 28 facing and engageableby the spherical balls 20.

A block or disc '30 has a flat surface enga eable with a 'fiat surfaceof the thrust member 22. The block '30 is connected to a piston 32'by apin '34 to prevent relative rotation between said bloc "and piston. Thepiston 32 is slidably fitted within ,a sleeve 36 having a tight fit witha bore 38 in the housing'l2. A pin 48 secured to the sleeve 36 extendsinto a slot 42 within the piston to prevent rotation of the pistonwhereby the pin also prevents rotation of the 101001130; The block 30 ismade of suitable anti-friction material such as graphite or carbon andcomprises an axial thrust bearing for transmitting the axial thrust ofthe rotating thrust member 22 to the non rotating-pistcntl The block ordisc 36 can be made of any material having a low coefficient of frictionrelative to the thrust member 22 and requiring no external lubrication.The pin 34 insures that all relative rotation occurs between the block39 and the rotating thrust member 22.

A fluid under pressure is supplied to the speed sensing mechanismthrough a conduit 42. From the conduit 42 said fluid is transmitted tothe space M behind the piston 32 through a passage 46, an annulus 28about the sleeve 36, a radial hole 59 through said sleeve, an annulus 52about the piston 32 and thence through radial holes 54 in said piston.As the piston 32 moves axially,

the upper edge of the annulus 52 (as viewed in the drawing) moves acrossthe hole 5!! thereby varying the extent to which said hole is uncovered.An outlet conduit 56 also communicates with the space 44 through apassage 58, an annular groove and slots 62 in the sleeve 36. There is acontinual leakage flow of fluid through the outlet conduitEB in orderthat movement of the piston 32 controlsthe pressure in the space A l byvarying the pressure drop through the portion of the hole 50 uncoveredby the piston annulus 52. The fluid pressure within the space 44 urgesthe conical face of the thrust member 22 against the balls 26. Aspring64 may also be provided for urging "the thrust member 22 against theballs 20. When the axial thrust exerted by the balls 20 against thethrust member 22 is less than the force of the spring 64, the piston 32moves downwardly to such an extent that the lower end of the pistonannulus 52 moves beyond the sleeve 36 whereupon the hole 58 is closedand the space behind the piston is vented through the restricted opening66.

With the above described construction, when the shaft I0 rotates theballs 20 rotate with said shaft and therefore said balls are urgedradially outwardly, by centrifugal forces acting thereon, against theconical face 28 of the thrust member 22. Accordingly the thrust member22 is urged axially by the axial component of the force exerted by theballs 2-9 against the conical face 28. This axial force or thrust istransmitted by the thrust member 2-2 through the block 33 to the piston32 and is opposed bythe fluid pressure in the space 'M acting againstsaid piston and in covered. This upward motion of the piston '32-continues until the pressure within the space 44 has increasedsuffi'ciently to again establish a balance. If the speed of rotation ofthe shaft in decreases, the axial thrust produced by the balls decreasesso that the piston is now moved downwardly by its spring 54 and by thefluid pressure within the space Mt until said piston covers the hole 50to an extent such that the pressure within said space is reducedsufficiently to again establish a balance. Thus the piston 32 alwaystakes an axial position such that the fluid pressure within the space 4%plus the pressure of the spring 6 3 always balances the axial thrustproduced by the balls 20. In this Way the piston 32 automatically movesto maintain a pressure within the space M which is a function of thespeed of rotation of the shaft 10.

Figure 2 is a schematic illustration of an application of the speedsensing mechanism l2 for controlling the speed of rotation of an engineindicated on the drawing by the block it. The shaft it is driven by theengine 70 and said engine is provided with means it, such as a valve,which is adjustable to vary the speed of rotation of the engine. As aspecific example the engine 70 and valve '42 may comprise the turbineand balanced speed control valve respectively, disclosed in copendingapplication Serial No. 57,144, filed C ctober 1948, now abandoned. Thefluid pressure automatically controlled by the speed sensing mechanismi2 is transmitted through the conduit 55 to one side of a piston iswhich is operatively connected to the means or valve 72, the other sideof said piston being vented. The piston i -l has a restricted leakagepath it to provide for the previously mentioned fluid ilow through theconduit In addition a spring it acts against the piston is to oppose thefluid pressure transmitted through the conduit 56 to said piston.Accordingly an increase in the output pressure of the speed sensingniechanisn'l 52, as a result of an increase in the speed of the shaftit), moves the piston it against the spring :73. This movement of thepiston is adjusts the member 72 in a direction for decreasing the speedof rotation of the engine it. A decrease in the output pressure of thespeed sensing mechanism produces an opposite adjustment of the speedregulating member l2.

If for example the speed of the shaft E of the engine it is to be heldbetween 40,000 and 44,000 revolutions per minute (R. P. M.) then thespring ti t is designed so that its spring force is equal to the axialthrust produced by the balls 20 at 40,000 E. P. M. In addition thepiston 32 and its ports are designed so that at or below 40,000 R. P. M.the pressure within the space is a minimum, that is said space isvented, and as the speed increases from 40,000 to 44,000 E. P. M. thehole 50 i progressively uncovered by the piston 32 until at 44,009 R. P.M. said hole is fully uncovered whereupon the pressure within the space64 is a maximum. Obviously, however, the spring 64 is not a necessarypart of the invention. For example, if the spring as were omitted thenthe fluid pressure within the space as could be proportional to thespeed of the shaft [0 throughout its. speed range instead of only withinthe upper portion or" the speed range. it is assumed that sufiicientiiuid pressure is available through the conduit 42 to balance the axialthrust at the maximum speed of the shaft 10.

It should be noted that the shaft guide member 16 and the thrust member22 all rotate at the same speed with the shaft 10 so that except for thesmall radial movements of the balls 20 there is no relative motion,sliding or rolling, between said balls and the surfaces engaged thereby.Accordingly there is no tendency for the balls to roll up the conicalsurface 28 except as a result of changes in the centrifugal forcesacting on said balls. This feature is quite important at the highrotative speeds herein contemplated.

While we have described our invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding our invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Weaim in the appended claim to cover all such modifications.

We claim as our invention:

Speed sensing mechanism comprising a housing; a rotatable first memberextending into said housing; a rotatable second member disposed withinsaid housing; means within said housing providing a rotationally rigiddriving connection between said members while permitting axial movementof said second member relative to said first member; at least one balldisposed within said housing between said members offset from the axisof rotation of said members; means for insuring rotation of said ballswith members about said axis; a conical surface on and oo-axial with oneof said members and engageable by each said ball so that the centrifugalforce acting on each said ball subjects said second member to an axialforce; a third member disposed within said housing cc-axial with andaxially movable with said second member; means within said housing forpreventing rotation of said third member; a thrust bearing said housingbetween said second and third members for transmitting axial motion ofsaid secon 'ile'fiibfll to said third member; means for supplying afluid under pressure into said housing for subjecting said third memberto a fluid pressure force opposing said axial force, said second andthird members being axially movable in response to unbalance of theforces thereon; and valve means disposed within said housing andautomatically controlled by axial movements of said third member forrespectively increasing or decreasing the magnitude of said fluidpressure in response to axial movements or said third member or oppositeto the direction of said axial force whereby the magnitude of said fluidpressure respectively increases and decreases with increase and decreasein the speed of rotation of first and second members.

HILLARD E. SAMUEL J. HALL. \WILLIAIM C. SCHAFFER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,013,222 Thomas Slept. 3, 1935 2,155,247 Warner Apr. 13, 19392,250,983 Adler July 29, 194-1 2,277,395 Franck Mar. 24., 194:22,336,654 Tippen Bee. 1 1-, 1943 2,402,972 Mitchell July 2, 19452,454,902 Warren Novv 30, 1948 FOREIGN PATENTS Number Country Date579,868 France or 1924

